1. Technical Field of the Invention
Embodiments of the present invention relate to a medium transport device that transports a medium such as a sheet of paper, a printing apparatus that is provided with such a device, and a liquid ejecting apparatus that ejects a liquid onto a medium.
2. Background Art
As a medium transport device that transports a medium such as a sheet of paper, a medium transport device that is configured so that an image capture unit is provided in a medium support unit that supports a medium, an image of the texture of a lower surface of a medium that passes over the medium support unit is captured by the image capture unit, and a transport weight of the medium is detected on the basis of the captured image, is known. In the medium transport device, an opening section for irradiating light from the image capture unit toward a lower surface of a medium is formed on a support surface of the medium support unit. Further, a light-transmitting member for allowing the transmission of light while suppressing the entry of foreign substances such as paper powder and dust into the inside of the image capture unit is disposed in the opening section.
As this kind of medium transport device, for example, the medium transport device of PTL 1 performs a template matching process that locates a position at which a degree of similarity with an image that was captured on a previous occasion is greatest while moving a template of a rectangular region that is set in advance over an image that is captured on a current occasion in order to detect a transport weight of the medium. That is, the medium transport device of PTL 1 calculates a distance in a transport direction of a position of a template in an image that was captured on a previous occasion and a position of a template in an image that is matched and captured on a current occasion as a transport weight of the medium.
As shown in FIG. 4 of PTL 1, in the medium transport device of PTL 1, an upper surface of the light-transmitting member that is disposed in the opening section of the medium support unit is flush with a support surface, and a focal position of the image capture unit is aligned with the support surface. That is, the medium transport device is adjusted so that the focal position of the image capture unit becomes an upper surface of the light-transmitting member.
In addition, as a liquid ejecting apparatus that ejects a liquid such as an ink from an ejecting unit onto a medium such as a sheet of paper, a liquid ejecting apparatus that is configured so that an image capture unit is provided in a medium support unit that supports a medium, an image of the texture of a lower surface of a medium that passes over the medium support unit is captured by the image capture unit, and a transport weight of the medium is detected on the basis of the captured image, is known. In this kind of liquid ejecting apparatus, an opening section for irradiating light from the image capture unit toward a lower surface of a medium is formed on a support surface of the medium support unit (for example, refer to PTL 1).
In this kind of liquid ejecting apparatus, for example, in a case in which a large amount of liquid is ejected onto a medium from the ejecting unit in the manner of that used during solid printing or the like, there are case in which the medium swells as a result of absorbing a large amount of liquid, and therefore, the medium after printing becomes wavy with respect to the support surface of the medium support unit, and so-called cockling is generated.
In such a case, there is a concern that portions of the medium that have become deformed in a bending manner in a direction that rises from the support surface due to the cockling phenomenon will come into contact with the ejecting unit.
In such an instance, as shown in FIG. 9, in this kind of liquid ejecting apparatus, a plurality of concave sections 102 are formed on a support surface 101 of a medium support unit 100, and suction holes 103 are formed on the support surface 101 at a plurality of points including a bottom surface region of a portion of the concave sections 102. Further, it is configured so that the medium is adsorbed to a support surface 101 side by driving a suction fan (not shown in the drawing) that is in communication with each suction hole 103.